Conventionally, there are proposed many pneumatic tires having a tread surface which is provided with a directional tread pattern the tire rotational direction of which is specified in one direction. In the pneumatic tires having such a directional tread pattern, there are pneumatic tires including a tread surface having circumferential grooves extending in a circumferential direction of the tire, and lateral grooves extending in a widthwise direction of the tire and disposed at given intervals in the tire circumferential direction to thereby define blocks in its shoulder regions (for example, see Unexamined Japanese Patent Application Publication No. 11-91313).
In recent years, circuit courses are opened up to general car users, and the users often have chances to make their cars run a circuit course. When running such a circuit course, a lateral acceleration acting during turning is much greater, compared with that in normal driving when running a public road, and irregular wear different from that in the normal driving is, therefore, created.
In the pneumatic tires having the above-mentioned directional pattern of blocks, the normal driving produces heel-and-toe wear such that the edge portions (stepping-in side edge portions), on a direction side of reverse rotation of the tire, of the blocks facing to the lateral grooves wear more slowly than the edge portions (kicking-out side edge portions) thereof on a direction side of rotation of the tire. Therefore, the inclination angles of the stepping-in side groove wall surfaces of the blocks are greater than the inclination angles of the kicking-out side groove wall surfaces thereof to increase rigidity of the stepping-in side edge portions, thereby suppressing heel-and-toe wear.
However, when running a circuit with such a tire, there is a problem of occurrence of irregular wear such that the kicking-out side edge portions of the blocks wear more slowly than the stepping-in side edge portions thereof.